diff --git a/core/java/android/os/StrictMode.java b/core/java/android/os/StrictMode.java
index 02b822a99f2ad..772845d4e6837 100644
--- a/core/java/android/os/StrictMode.java
+++ b/core/java/android/os/StrictMode.java
@@ -817,6 +817,9 @@ public final class StrictMode {
 
             /** @hide */
             public @NonNull Builder permitActivityLeaks() {
+                synchronized (StrictMode.class) {
+                    sExpectedActivityInstanceCount.clear();
+                }
                 return disable(DETECT_VM_ACTIVITY_LEAKS);
             }
 
@@ -2586,8 +2589,10 @@ public final class StrictMode {
                 return;
             }
 
+            // Use the instance count from InstanceTracker as initial value.
             Integer expected = sExpectedActivityInstanceCount.get(klass);
-            Integer newExpected = expected == null ? 1 : expected + 1;
+            Integer newExpected =
+                    expected == null ? InstanceTracker.getInstanceCount(klass) + 1 : expected + 1;
             sExpectedActivityInstanceCount.put(klass, newExpected);
         }
     }
diff --git a/services/tests/wmtests/AndroidManifest.xml b/services/tests/wmtests/AndroidManifest.xml
index f382fbae9280f..30df0d4b4ad91 100644
--- a/services/tests/wmtests/AndroidManifest.xml
+++ b/services/tests/wmtests/AndroidManifest.xml
@@ -62,6 +62,7 @@
                   android:resumeWhilePausing="true"/>
         <activity android:name="com.android.server.wm.ScreenDecorWindowTests$TestActivity"
                   android:showWhenLocked="true" android:allowEmbedded="true"/>
+        <activity android:name="com.android.server.wm.ActivityLeakTests$DetectLeakActivity" />
     </application>
 
     <instrumentation
diff --git a/services/tests/wmtests/src/com/android/server/wm/ActivityLeakTests.java b/services/tests/wmtests/src/com/android/server/wm/ActivityLeakTests.java
new file mode 100644
index 0000000000000..bd6ac58c24458
--- /dev/null
+++ b/services/tests/wmtests/src/com/android/server/wm/ActivityLeakTests.java
@@ -0,0 +1,184 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server.wm;
+
+import static android.content.Intent.FLAG_ACTIVITY_MULTIPLE_TASK;
+import static android.content.Intent.FLAG_ACTIVITY_NEW_DOCUMENT;
+import static android.content.Intent.FLAG_ACTIVITY_NEW_TASK;
+
+import static androidx.test.platform.app.InstrumentationRegistry.getInstrumentation;
+
+import static org.junit.Assert.assertFalse;
+
+import android.app.Activity;
+import android.app.Instrumentation;
+import android.content.Context;
+import android.content.Intent;
+import android.os.Bundle;
+import android.os.Debug;
+import android.os.StrictMode;
+import android.os.strictmode.InstanceCountViolation;
+import android.util.Log;
+
+import org.junit.After;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Tests for Activity leaks.
+ *
+ * Build/Install/Run:
+ *     atest WmTests:ActivityLeakTests
+ */
+public class ActivityLeakTests {
+
+    private final Instrumentation mInstrumentation = getInstrumentation();
+    private final Context mContext = mInstrumentation.getTargetContext();
+    private final List<Activity> mStartedActivityList = new ArrayList<>();
+
+    @After
+    public void tearDown() {
+        mInstrumentation.runOnMainSync(() -> {
+            // Reset strict mode.
+            StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder().build());
+        });
+        for (Activity activity : mStartedActivityList) {
+            if (!activity.isDestroyed()) {
+                activity.finish();
+            }
+        }
+        mStartedActivityList.clear();
+    }
+
+    @Test
+    public void testActivityLeak() {
+        final Bundle intentExtras = new Bundle();
+        intentExtras.putBoolean(DetectLeakActivity.ENABLE_STRICT_MODE, true);
+        final DetectLeakActivity activity = (DetectLeakActivity) startActivity(
+                DetectLeakActivity.class, 0 /* flags */, intentExtras);
+        mStartedActivityList.add(activity);
+
+        activity.finish();
+
+        assertFalse("Leak found on activity", activity.isLeakedAfterDestroy());
+    }
+
+    @Test
+    public void testActivityLeakForTwoInstances() {
+        final Bundle intentExtras = new Bundle();
+
+        // Launch an activity, then enable strict mode
+        intentExtras.putBoolean(DetectLeakActivity.ENABLE_STRICT_MODE, true);
+        final DetectLeakActivity activity1 = (DetectLeakActivity) startActivity(
+                DetectLeakActivity.class, 0 /* flags */, intentExtras);
+        mStartedActivityList.add(activity1);
+
+        // Launch second activity instance.
+        intentExtras.putBoolean(DetectLeakActivity.ENABLE_STRICT_MODE, false);
+        final DetectLeakActivity activity2 = (DetectLeakActivity) startActivity(
+                DetectLeakActivity.class,
+                FLAG_ACTIVITY_MULTIPLE_TASK | FLAG_ACTIVITY_NEW_DOCUMENT, intentExtras);
+        mStartedActivityList.add(activity2);
+
+        // Destroy the activity
+        activity1.finish();
+        assertFalse("Leak found on activity 1", activity1.isLeakedAfterDestroy());
+
+        activity2.finish();
+        assertFalse("Leak found on activity 2", activity2.isLeakedAfterDestroy());
+    }
+
+    private Activity startActivity(Class<?> cls, int flags, Bundle extras) {
+        final Intent intent = new Intent(mContext, cls);
+        intent.addFlags(flags | FLAG_ACTIVITY_NEW_TASK);
+        if (extras != null) {
+            intent.putExtras(extras);
+        }
+        return mInstrumentation.startActivitySync(intent);
+    }
+
+    public static class DetectLeakActivity extends Activity {
+
+        private static final String TAG = "DetectLeakActivity";
+
+        public static final String ENABLE_STRICT_MODE = "enable_strict_mode";
+
+        private volatile boolean mWasDestroyed;
+        private volatile boolean mIsLeaked;
+
+        @Override
+        protected void onCreate(Bundle savedInstanceState) {
+            super.onCreate(savedInstanceState);
+            if (getIntent().getBooleanExtra(ENABLE_STRICT_MODE, false)) {
+                enableStrictMode();
+            }
+        }
+
+        @Override
+        protected void onDestroy() {
+            super.onDestroy();
+            getWindow().getDecorView().post(() -> {
+                synchronized (this) {
+                    mWasDestroyed = true;
+                    notifyAll();
+                }
+            });
+        }
+
+        public boolean isLeakedAfterDestroy() {
+            synchronized (this) {
+                while (!mWasDestroyed && !mIsLeaked) {
+                    try {
+                        wait(5000 /* timeoutMs */);
+                    } catch (InterruptedException ignored) {
+                    }
+                }
+            }
+            return mIsLeaked;
+        }
+
+        private void enableStrictMode() {
+            StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder()
+                    .detectActivityLeaks()
+                    .penaltyLog()
+                    .penaltyListener(Runnable::run, violation -> {
+                        if (!(violation instanceof InstanceCountViolation)) {
+                            return;
+                        }
+                        synchronized (this) {
+                            mIsLeaked = true;
+                            notifyAll();
+                        }
+                        Log.w(TAG, violation.toString() + ", " + dumpHprofData());
+                    })
+                    .build());
+        }
+
+        private String dumpHprofData() {
+            try {
+                final String fileName = getDataDir().getPath() + "/ActivityLeakHeapDump.hprof";
+                Debug.dumpHprofData(fileName);
+                return "memory dump filename: " + fileName;
+            } catch (Throwable e) {
+                Log.e(TAG, "dumpHprofData failed", e);
+                return "failed to save memory dump";
+            }
+        }
+    }
+}